Structural and functional assessment of trabecular and cortical bone by micro magnetic resonance imaging

Abstract

Osteoporosis is a multifactorial disorder of bone mineral homeostasis affecting the elderly. It is a major public health issue with significant socioeconomic consequences. Recent findings suggest that bone loss-the key manifestation of the disease-is accompanied by architectural deterioration, both affecting the bone's mechanical competence and susceptibility to fracture. This article reviews the potential of quantitative micro MRI (-MRI), including a discussion of the technical requirements for image acquisition, processing, and analysis for assessing the architectural implications of osteoporosis and as a means to monitor the response to treatment. With current technology, the resolution achievable in clinically acceptable scan times and necessary signal-to-noise ratio (SNR) is comparable to trabecular thickness. This limited spatial resolution regime demands processing and analysis algorithms designed to operate under such limiting conditions. It is shown that three different classes of structural parameters can be distinguished, characterizing scale, topology, and orientation. There is considerable evidence that osteoporotic bone loss affects all three classes but that topological changes, resulting from conversion of trabecular plates to rods, with the latter's eventual disconnection, are particularly prominent. Clinical applications discussed can be divided into those dealing with assessment of osteoporotic fracture risk as opposed to the study of the effect of disease progression and regression in response to treatment. Current data suggest that noninvasive assessment of cortical and trabecular bone (TB) architecture by -MRI may provide new surrogate endpoints to assess the efficacy of intervention in osteoporosis treatment and prevention.

Measurements of mobile and bound water by nuclear magnetic resonance correlate with mechanical properties of bone

“…One previous study investigated connections between architectural indices of trabecular bone (as determined by MRI) and bone strength [54], while another related water content (as determined by NMR-derived diffusion characteristics of exchangeable water) to bone density and strength in an animal model of hypomineralization [49]. MRI studies of bone have been focused on assessing the structure or architecture of trabecular and cortical bone (see review by Wehrli for details [57]), but recently, water volume fraction in the mid-shaft of human tibiae was quantified by analyzing T 2 protons with a 3 Tesla, clinical MRI scanner [58]. The effect of aging or water distribution however was not a focus in either of these studies, as it was here.…”

“…The 18 male donors had no known bone disease. Based on donor age, the femurs were divided into two groups: middle aged included 8 ages of 47,49,49,51,55,57,59, and 59 years, while the elderly included 10 ages of 67, 69, 76, 76, 77, 77, 79, 79, 81, and 87 years. Cut from the medial quadrant of each mid-diaphysis, a longitudinal strip of bone was machined, while maintaining hydration, into a standard paralellelepiped specimen such that the osteons ran in the direction of the long axis.…”

Risk of Fracture and Prevention and Treatment of Osteoporosis

“…Bone macro-architecture refers to whole bone geometry such as bone size and shape. Bone micro-architecture includes cortical microarchitecture described by cortical porosity and thickness, and trabecular micro-architecture described by trabecular scale (i.e., bone volume fraction, trabecular thickness, number and separation), trabecular topology (i.e., trabecular integrity, shape and connectively), and trabecular orientation [9,10].…”

Multiscale modelling and nonlinear finite element analysis as clinical tools for the assessment of fracture risk

“…Depending on the scanning requirements, it can be used to significantly reduce acquisition time, causing fewer motion artefacts, or to decrease the slice thickness to isotropic resolutions of about 1 mm. Much progress has been made in the field of magnetic resonance imaging (MRI) (Wehrli 2007;Majumdar 2008), a technique that is not only non-invasive but also nonionizing. However, the long acquisition times required for bone microstructural imaging and the challenging segmentation of hard and soft tissue currently prevent its use for large-scale clinical studies.…”